The goal of this application is to understand the mechanisms controlling episodic release of LH and GnRH during the ovarian cycle, and to determine how these mechanisms are altered during seasonal anestrus in the ewe. In Aim 1, fos and TH mRNA expression with A14/15 DA neurons will be used to examine activation of these cells by E2, and microdialysis will be used to examine DA release in the median eminence (ME). Aim 2 will seek to identify the estrogen (E)-responsive cells that mediate the actions of E2 on DA neuronal activity using a variety of approaches. Aim 3 will address mechanisms of action of progesterone (P) negative feedback during the luteal phase of the ovarian cycle, focusing on beta-endorphin and GABA as potential mediators.